Anti-reflective sputtering stack with low Rv and low Ruv

Abstract

The present invention provides a UV antireflective coating stack for ophthalmic lenses. The antireflective coating stack is deposited by sputtering, which lowers the reflectivity of the antireflective stack in the UV range and maintains low reflectivity in the visible range. The antireflective coating stack offers improved thermo-mechanical performance as compared to evaporation-based UV antireflective stacks.

Claims

1. An ophthalmic lens comprising: a transparent substrate with a front face and a rear face, the rear face being successively coated with a hard-coat having a refractive index less than or equal to 1.6, and a multilayered antireflective coating comprising a stack of at least one layer A having a refractive index n.sub.A less than 1.55, and of at least one layer B having a refractive index n.sub.B greater than or equal to 1.55, wherein the mean reflection factor Ruv on the rear face in the range 280 nm to 380 nm, weighted by the W(λ) function defined according to the ISO 13666:1998 standard, is less than or equal to 5% for an angle of incidence of 35°, and the multilayered antireflective coating has been deposited by sputtering, and wherein the ratio (sum of the physical thicknesses of the layers having a refractive index less than 1.55 in the multilayered antireflective coating/sum of the physical thicknesses of the layers having a refractive index equal to or greater than 1.55 in the multilayered antireflective coating) is less than 0.9, and wherein the multilayered antireflective coating the following layers listed in order of proximity to the hard coat: a first layer with a thickness ranging from 18-34 nm having a refractive index greater than 1.55; a second layer with a thickness ranging from 11-23 nm having a refractive index lower than or equal to 1.55; a third layer with a thickness ranging from 90-120 nm having a refractive index greater than 1.55; and a fourth layer with a thickness ranging from 65-80 nm having a refractive index lower than or equal to 1.55.

2. The ophthalmic lens according to claim 1, wherein the mean light reflection factor on the rear face in the visible region Rv, defined between 380 and 780 nm in the ISO 13666:1998 standard, is less than or equal to 2%.

3. The ophthalmic lens according to claim 2, wherein the mean light reflection factor on the rear face in the visible region Rv is ranging from 0.9% to 2%.

4. The ophthalmic lens according to claim 2, wherein the mean light reflection factor on the rear face in the visible region Rv is ranging from 1% to 2%.

5. The ophthalmic lens according to claim 1, wherein the multilayered antireflective coating has a hue angle ranging from 275° to 325° at an angle of incidence of 15°.

6. The ophthalmic lens according to claim 1, wherein a chroma of the multilayered antireflection coating is less than 15 for an angle of incidence of 15°.

7. The ophthalmic lens according to claim 1, wherein: layer A is the outermost layer of the multilayered antireflective coating, layer B is adjacent to said layer A and the physical thickness of said outermost layer A is less than the physical thickness of said adjacent layer B.

8. The ophthalmic lens according to claim 1, further comprising a sublayer adjacent to the multilayered antireflective coating having a refractive index nsub less than 1.55.

9. The ophthalmic lens according to claim 1, wherein layer A comprises at least one oxide chosen from silicon oxides and mixtures of silicon oxides and aluminum oxide.

10. The ophthalmic lens according to claim 1, wherein layer B comprises at least one material selected from the group consisting of zirconia (ZrO.sub.2), titanium dioxide (TiO.sub.2), tantalum pentoxide (Ta.sub.2O.sub.5), niobium oxide (Nb.sub.2O.sub.5), alumina (Al.sub.2O.sub.3), praseodymium oxide (Pr.sub.2O.sub.3), praseodymium titanate (PrTiO.sub.3), silicon nitride.

11. The ophthalmic lens according to claim 10, wherein layer B comprises Si.sub.3N.sub.4.

12. The ophthalmic lens according to claim 1, further comprising a layer C having a refractive index n.sub.C, wherein layers A, B and C are adjacent in that order and n.sub.C is greater than 1.55 and less than n.sub.B.

13. The ophthalmic lens according to claim 1, having a critical temperature greater than or equal to 60° C.

14. The ophthalmic lens according to claim 1, further comprising a hard-coat having a refractive index less than 1.55.

15. The ophthalmic lens according to claim 1, further comprising a hard-coat having a refractive index less than 1.5.

16. The ophthalmic lens according to claim 1, wherein layer A comprises at least one oxide chosen from silica or a mixture of silica and aluminum oxide.

17. The ophthalmic lens according to claim 1, wherein multilayered antireflective coating comprises the following layers listed in order of proximity to the hard coat: a first layer with a thickness ranging from 18-25 nm having a refractive index greater than 1.55; a second layer with a thickness ranging from 15-20 nm having a refractive index lower than or equal to 1.55; a third layer with a thickness ranging from 90-120 nm having a refractive index greater than 1.55; and a fourth layer with a thickness ranging from 65-80 nm having a refractive index lower than or equal to 1.55.

18. A method for manufacturing an ophthalmic lens comprising the steps of: providing a transparent substrate with a front face and a rear face; applying on the rear face a hard-coat having a refractive index less than or equal to 1.6 and depositing by sputtering a multilayered antireflective coating comprising a stack of at least one layer A having a refractive index n.sub.A less than or equal to 1.55 and of at least one layer B having a refractive index n.sub.B greater than 1.55; and obtaining said ophthalmic lens having a mean reflection factor in the range 280 nm to 380 nm on the rear face that is less than or equal to 5% for an angle of incidence of 35°; wherein the ratio (sum of the physical thicknesses of the layers having a refractive index less than 1.55 in the multilayered antireflective coating/sum of the physical thicknesses of the layers having a refractive index equal to or greater than 1.55 in the multilayered antireflective coating) is less than 0.9, and wherein the multilayered antireflective coating the following layers listed in order of proximity to the hard coat: a first layer with a thickness ranging from 18-34 nm having a refractive index greater than 1.55; a second layer with a thickness ranging from 11-23 nm having a refractive index lower than or equal to 1.55; a third layer with a thickness ranging from 90-120 nm having a refractive index greater than 1.55; and a fourth layer with a thickness ranging from 65-80 nm having a refractive index lower than or equal to 1.55.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The following drawing illustrate by way of example and not limitation.

(2) FIG. 1 is a graph wherein % Ruv values are reported as a function of hard coat refractive index.

(3) FIG. 2 is an exploded sectional view illustrating an embodiment of an ophthalmic lens as disclosed herein.

DETAILED DESCRIPTION

(4) Various features and advantageous details are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements will be apparent to those of ordinary skill in the art from this disclosure.

(5) In the following description, numerous specific details are provided to provide a thorough understanding of the disclosed embodiments. One of ordinary skill in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

(6) It has been found that an antireflective stack deposited by sputtering decreases reflection in the UV range and the visible range and offers improved thermomechanical properties as compared to evaporation-bases antireflective stacks.

(7) The colorimetric coefficients (including hue and chroma) of the antireflective-coated ophthalmic lenses of the invention are defined in the international colorimetric system CIE L*a*b* 1976, using standard observer 10° and standard illuminant D65 and are calculated between 380 and 780 nm at an angle of incidence of 15°. When the stacks are applied on the convex side of the lenses only, the optical property measurements are made on the convex side to evaluate slight changes from theoretical (design target) to experimental values. It has been shown that the properties of stacks deposited either on the front or the back side are similar.

EXAMPLES

(8) Lens Preparation

(9) 1. Lens Substrates

(10) ORMA® lenses: Finished single vision uncoated plano lenses, 6 base, in ORMA® (polymer of diethylene glycol bis (allylcarbonate)). PC lenses: Finished single vision uncoated plano lenses, 6 base, in polycarbonate (PC). The PC lenses can be initially naked (uncoated) PC substrates or commercial PC lenses having initially a PDQ™ coating that is stripped before applying primer and/or hard coating. As classically known in the art, the base of a lens corresponds to the curvature (expressed in dioptries) of the front face of a lens base: base=530/R in mm (R=radius of curvature of the anterior surface of spectacle lens).

(11) 2. Primer Composition

(12) 2.1 List of Used Primers:

(13) Primer 1: Witcobond® W234 aliphatic polyurethane dispersion.

(14) Primer 2: high refractive polyurethane dispersion with a high refractive index colloid. Refractive index of the cured primer: 1.63.

(15) 2.2 Deposition Process of Primer

(16) Both convex (Cx) and concave (Cc) sides of the lenses are coated in a dip coating process. Primer 1:

(17) ORMA® or PC lenses as defined in 1) above, are first dipped in a bath of primer 1, then removed and heated at 75° C. for 16 minutes followed by 16 minutes ambient cooling before subsequent hard coat application. The thickness of the primer is 1.0±0.15 microns.

(18) Primer 2:lenses are first dipped in a bath of primer 1, then removed and heated at 75° C. for 16 minutes followed by 16 minutes ambient cooling before subsequent hard coat application. The thickness of the primer is 0.8±0.10 microns.

(19) 3. Hard Coats

(20) 3.1 List of Used Hard Coats

(21) Hard coat 1 (HC1): Hard coating composition corresponding to example 3 of EP614957 (refractive index of cured hard coat: 1.48).

(22) Hard coat 2 (HC1): Commercial UV curable abrasion resistant coating—Hard coat HT850™ from LTI (refractive index of hard coat 2 is 1.515 at 550 nm).

(23) Hard coat 3: High refractive index hard coat: (refractive index=1.595) (Used in examples of FIG. 1).

(24) 3.2 Deposition Process of Hard Coats

(25) 3.2.1 Process of Deposition of Hard Coat 1

(26) Lenses that have been previously coated by primer 1 in 2.2 above are dipped in a bath of hard coat composition 1, removed and heated at a temperature of 75° C. for 16 minutes. The lenses are then post-cured in a standard curing DIMA™ oven at 115° C. for 25 minutes. After post-curing, the lenses are kept in a holding oven at 60° C. for 1-2 hours. The thickness of hard coat 1 is 3.6±0.4 microns.

(27) Process of Deposition of Hard Coat 2 (HT850™)

(28) Lenses are hand washed and then coated on Cx side only with HT850™ UV curable coating in a Magna-spin™ spin coating machine (available from Satisloh). The lenses were UV cured inside the Magna-spin machine. The UV dosage for curing is 1.1±0.1 J/cm.sup.2. The thickness of hard coat 2 is 4.5±0.2 microns.

(29) 4. AR Stacks and Deposition Process

(30) 4.1-Deposition Process by Evaporation (Comparative)

(31) The lenses are removed from the holding oven and put into a Balzers BAK760 AR coating chamber. AR stack1 (AR1) is deposited in this order: 34 nm ZrO.sub.2 (layer closest to the lens substrate) 21 nm SiO.sub.2 103 nm ZrO.sub.2 79 nm SiO.sub.2 (layer of the stack furthest from lens substrate)

(32) TABLE-US-00002 Starting Deposition Pressure Ion Gun Step Description Material Rate, nm/s mbar Gas Flow Parameters 1 Ion Plasma Clean/ None None   3 × 10.sup.−5 Argon (25 sccm) 100 V, 1 A, Surface Preparation 60 secs 2 Deposition ZrO.sub.2 ZrO 0.35 8.0 × 10.sup.−5 Oxygen (10 sccm) — 3 Deposition SiO.sub.2 SiO.sub.2 0.60 7.0 × 10.sup.−5 None — 4 Deposition ZrO.sub.2 ZrO 0.30 7.0 × 10.sup.−5 Oxygen (10 sccm) — 5 Deposition SiO.sub.2 SiO.sub.2 1.0 7.0 × 10.sup.−5 None —

(33) 4.2 Sputtering Deposition Process

(34) The lenses from steps 3.2.1 or 3.2.2 are put into a SP200™ sputter machine from Satisloh and are deposited according to the folllowing steps: If lenses are coated by hard coat 2, they are put into the sputtering machine immediately after they had been hard coated. Only the Cx side of the lenses was coated as all the following tests performed are done on Cx side of lenses.

(35) The deposited stack is AR2 21 nm Si.sub.3N.sub.4 (1st layer in contact with hard coat) 16 nm SiO.sub.2 109 nm Si.sub.3N.sub.4 73 nm SiO.sub.2

(36) TABLE-US-00003 Starting Deposition Pressure Gas Flow, Plasma Step Description Material Rate, nm/s mbar sccm Parameters 1 Ion Plasma Clean/ None None   3 × 10.sup.−3 Argon: 25-50 Power 1500 W Surface Preparation Volt 340-380 V 2 Deposition Si.sub.3N.sub.4 Silicon 0.70-0.80 1.0 × 10.sup.−3 Nitrogen = Power 2000 W 9-12.0 Volt 490-510 V 3 Deposition SiO.sub.2 Silicon 1.15-1.30 1.0 × 10.sup.−3 Oxygen = Power 1500 W 10.8-11.5 Volt 510-530 V 4 Deposition Si.sub.3N.sub.4 Silicon 0.70-0.80 1.0 × 10.sup.−3 Nitrogen = Power 2000 W 9 to 12.0 Volt 490-510 V 5 Deposition SiO.sub.2 Silicon 1.15-1.30 1.0 × 10.sup.−3 Oxygen = Power 1500 W 10.8-11.5 Volt 510-530 V

(37) AR3: Deposited layers: 58 nm Silicon Oxynitride with index of 1.76 at 550 nm (1st layer in contact with hard coat) 96 nm Si.sub.3N.sub.4 73 nm SiO.sub.2

(38) TABLE-US-00004 Starting Deposition Pressure Gas Flow, Plasma Step Description Material Rate, nm/s mbar sccm Parameters 1 Ion Plasma Clean/ None None   3 × 10.sup.−3 Argon = 50 Power 1500 W Surface Preparation Volt 340-380 V 2 Deposition SiO.sub.xNy Silicon 0.75-0.85 1.0 × 10.sup.−3 Nitrogen = Power 2000 W 8 to 9 and Volt 490-510 V Oxygen = 1.8-2.1 3 Deposition Si.sub.3N.sub.4 Silicon 0.70-0.80 1.0 × 10.sup.−3 Nitrogen = Power 2000 W 9 to 12.0 Volt 490-510 V 4 Deposition SiO.sub.2 Silicon 1.15-1.30 1.0 × 10.sup.−3 Oxygen = Power 1500 W 10.8-11.5 Volt 510-530 V

(39) AR4 Deposited layers: 18 nm Si.sub.3N.sub.4 (1st layer in contact with hard coat) 23 nm SiO.sub.2 111 nm Si.sub.3N.sub.4 76 nm SiO.sub.2

(40) AR5 Deposited layers: 21 nm Si.sub.3N.sub.4 (1st layer in contact with hard coat) 11 nm SiO.sub.2 111 nm Si.sub.3N.sub.4 77 nm SiO.sub.2

(41) AR4 and AR5 are deposited using the same process as AR2, with only the thickness differing.

(42) 5.Hydrophobic Coatings

(43) OF210™ from Optron or Aulon™ from Satisloh are deposited on the previously applied AR.

(44) Process of deposition of OF210™ (in a Balzers BAK760 AR coating chamber).

(45) TABLE-US-00005 Hydrophobic Layer OF210 ™ Rate ~0.1 nm/s Pressure: Deposition (variable) 7.7 × 10.sup.−6 mbar

(46) Process of deposition of Aulon™:

(47) The hydrophobic layer used is Aulon™ M supplied by Satisloh. The hydrophobic layer comes impregnated in a single use disposable cloth tissue inside a sealed packet. For application the cloth tissue is removed from the packet and is applied by circular motion on the surface of the coated surface. Once a uniform layer is formed any additional hydrophobic forms beads on the surface. Hydrohobic coated lens surface is left at room temperature in open air for 15 minutes. After this the lens is rinsed under water and excess hydrophobic is washed off by using a mild soap.

(48) Examples are prepared using different primer, hard coats and stacks. They are summarized in tables. 1 and 2 with their optical properties:

(49) Effect of Hard Coat Index

(50) Several coatings were prepared with variable hard coat index and the corresponding % Ruv values are reported as a function of hard coat index (FIG. 1). Lowering the index of the hard coat is beneficial to the Ruv.

(51) Examples are prepared using different primers, hard coats and stacks. They are summarized in Table 3 with their critical temperature properties.

(52) One of the improvements seen with the coated lenses of the invention using the sputtering process is higher critical temperature.

(53) Critical Temperature Test

(54) The lens is placed in an oven heated at a temperature of 50° C. for one hour. The lens is then removed from the oven and the appearance of the substrate is visually evaluated. When the substrate has no crack, the set temperature of the oven is increased by 10° C. and the test is repeated. The critical temperature is then defined as that at which the AR is cracked. Examples were prepared using different primer, hard coats and stacks. The table below lists the stacks and their mechanical properties:

(55) TABLE-US-00006 TABLE 1 Hard Deposition h C Rv Ruv35° Substrate coat sublayer Stack method (hue) (chroma) (%) (%) Example 1* PC HC2 None AR2 147° 9.3  1.31  2.75 (Design- target) Example 1* PC HC2 None Idem Sputtering 149° ± 6°   7.8 ± 0.09 1.51 ± 0.08 3.76 ± 0.25 (Experimental) Example 1 Example 2* PC HC2 None AR2 313° 7.8 0.6 1.7 (Design- target) Example 2* PC HC2 None Idem Sputtering 321 ± 17° 7.9 ± 1.6 1.2 ± 0.1 1.64 ± 0.12 (Experimental) Example 2 Example 3* PC HC2 Yes 100 nm AR2 140° 9.6  0.93  2.33 (Design thickness target) (SiO.sub.2) Example 3* PC HC2 None Idem Sputtering 140 ± 8°  8.2 ± 1.5 1.4 ± 0.2  3.4 ± 0.35 (Experimental) Example 3 Example 4* PC HC2 None AR3 140 10.4  1.3 3.7 (Design target) Example4* PC HC2 None Idem Sputtering 147 ± 11° 11.9 ± 0.9  1.56 ± 0.3   3.1 ± 0.74 (Experimental) Example 4 Comparative PC HC2 None AR1 Evaporation 135 7   0.8 3.1 Example 1** *Samples having an Aulon ™ hydrophobic top coat deposited in direct contact to the AR stack. **Samples having an OF210 ™hydrophobic top coat deposited in direct contact with the AR stack

(56) TABLE-US-00007 TABLE 2 Ruv Deposition 35° Substrate Hard coat Sublayer Stack method h (hue) C (chroma) Rv (%) (%) Example 5* PC HC2 None AR2 147° 9.3 1.31 2.75 (Design-Target) Example 5* PC HC2 None AR2 Sputtering 149° +/− 6° 7.8 +/− 0.09 1.51 +/− 0.08 3.76 ± 0.25 (Experimental) Example 6* PC Primer 1/ None AR4 143° 8.3 1.06 2.50 (Design-Target)* HC1 Example 6* Primer 1/ None AR4 Sputtering 131 ± 6.0  6.4 ± 0.70 0.92 ± 0.05  3.2 ± 0.16 (Experimental) HC1 Example 7* PC Primer 2/ None AR5 140° 10.1  1.20 3.50 HC2 Example 7* PC Primer 2/ None AR5 Sputtering 144 ± 6.0 8.8 ± 1.0 1.17 ± 0.12 4.90 (Experimental) HC2 *Samples having an Aulon ™ hydrophobic top coat deposited in direct contact to the AR stack. **Samples having an OF210 ™hydrophobic top coat deposited in direct contact with the AR stack

(57) TABLE-US-00008 TABLE 3 Critical Critical Critical Temperature Temperature Temperature Examples Substrate AR Process for AR   1 week    3 weeks    5 weeks deposition Example 8 ORMA ® Primer AR2* sputtering 80° C. 80° C. 1/HC1 Comparative ORMA ® Primer AR1** Evaporation 50° C. 50° C. example 1 1/HC1 Example 9 ORMA ® HC2 AR2* sputtering 90° C. Comparative ORMA ® HC2 AR1** Evaporation 80° C. Example 2 Example 10 PC Primer AR2* Sputtering 120° C. 1/HC1 Comparative PC Primer AR1** Evaporation  80° C. example 3 1/HC1 *Samples having an Aulon ™ hydrophobic top coat deposited in direct contact to the AR stack **Samples having an OF210 ™hydrophobic top coat deposited in direct contact with the AR stack

(58) The critical temperature was evaluated with stacks on convex side only. (Critical temperature of the stacks on a back concave side are the same or very close).

RESULTS

(59) One of the improvements seen with the coated lenses of the invention using the sputtering process is higher critical temperature.

(60) Improved critical temperature was observed on PC HC1 with AR deposited by sputtering as compared to evaporation.

(61) Critical temperature seen on Orma® substrate are shown above. Important differences are seen on Orma® with Primer 1+hard coat 1. On Orma® lenses with hard coat 2, the differences are lower but clearly significant. The improvement of critical temperature is very important on PC lenses.

(62) This invention can be used by companies that are familiar with sputtering technology using the SP200 machine. The AR stack with sputtering can also be used in small labs with AR volumes of 100-200 lenses/day.

(63) The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.